Electron discharge device



Out:o 15, 1946. c. s. BULL 2,409,417

ELECTRON DISCHARGE DEVICE- Filed May 29, 1944 I I'NVENTOR. [5900 55970fiz/u 19 7-1-0 mwsy Patented Oct. 15, 1946 ELscrRoN DISCHARGE ncvicrCabotSeaton Bull, Hillingdon, England, assignor to Electric and MusicalIndustries Limited.

Application May 29, 1944, Serial No. 537,354;

In Great Britain June-21, 1941 (Cl. 315-a-6) Claims. 1.

My invention relatesv to high frequency electric circuits and toelectron discharge devices employing hollow resonators for use in suchcircuits.

It has been proposed to use such a hollow resonator as a tuned circuitand control electrode in a conventional triode, a screened grid orsimilar valve. In such a case the input signals are fed to the hollowresonator and the aperture in the hollow resonator which may or. may notbe provided with agridthrough which the beam passes, serves. to controlthe flow of electrons in much the sameway asthe control grid in aconventional valve.

I have found, however, that the stream of electrons passing through thegrid or aperture ives rise to a noise which is not encountered in theconventional type of valve. The electrons pass ing from the cathodetowards the grid or aperture induce a charge on the interior surface ofthe hollow resonator and once the electrons pass through the grid oraperture they have little or nofurther influence on the resonator withthe result that the induced charge discharges in an oscillatory manner.

the circuit and consequently the noise-to-signal ratio is not so good aswith the conventional arrangement of electron discharge device.

It is an object of the present invention to provide a high frequencyelectric circuitincludin an electron discharge device having a controlelectrode in which undesired effects arising from the high frequencyoperation are reduced.

A further object of the invention is to provide cathode and an anode anda control electrode for electrons passing between said cathode and saidanode, and including; means so connected and disposed as to be capableof deriving high frequency energy from electrons in the space betweensaid controlelectrode and said anode, the arrangement being such thatsaid energy will set up effects at said control electrode which whollyorpartly neutralize undersired high frequency effects occurring at saidcontrol electrode due to th passage of said electrons.

According to a further feature of the invention,

This discharge which is set, up by each electron constitutesa noisepower in 2 there is provided an electron discharge device comprisingmeans for providing an electron beam and a pair of hollow resonatorsthrough which said beam can be caused to pass, in succession,

said resonators being so coupled together that noise currents set up bythe passage of an elec-i.

tron through the first resonator are reduced or substantiallyneutralized by the noise currents set up by the passage of that electronthrough the second resonator.

In order that the said invention may be clearly understood and readilycarried into effect, the same will now be more fully described withref.-

erence to the drawing accompanying, the speci fication, in which:

Figure 1 is a schematic longitudinal section of The device according tothe invention shown in Figure 1 comprises a cathode I, an anode 8 and ahollow resonator 9 which constitutes the input circuit and will normallybe tuned to resonate at a suitable frequency depending upon thefrequency of the signals to be applied to the device. The hollowresonator 9 has the crosssection shown, and is of toroidal form and theaperture through which the electrons pass from 1 the cathode l to theanode 8 is covered by a grid l0 although in some cases this grid may beomitted. For the purpose of reducing noise current induced in theresonator 9 by the passage of the beam, a further hollow resonator II isprovided,

one wall of which is common with the wall of the resonator 9 containingthe grid lll. With such an arrangement an electron leaving the cathode land passing through the grid It leaves a negative charge on the side ofthe grid closing resonator ii and gives rise to an oscillatory dischargeor noise current. On passing through grid it! and resonator ll, thiselectron will give rise: to a further oscillatory discharge ina similarmanner, the two resonators beingcoupled together; so that the energyderived from the electron in the space within the second resonator isapplied to the first resonator 9 in such manner that the resultant noisecurrent therein is reduced or completely neutralized so that no noisevoltages are set up. on said control electrode due to. the passage ofelectrons between the anode and thecathode, The coupling between theresonators 9 and II in the example shown in Figure 1 is effected by theprovision of a pair of coupling loops I2 and I3 connected in series withthe source of input signals, the loops being reversed with respect toeach other. In the arrangement shown in Figure 2 of the drawing,however, the input signals are applied to the resonator 9 via a separatecoupling loop I 4 and the two resonators 9 and II are coupled togetherby the reverse coupling loop I5, as shown. It will be understood thatalthough the second resonator serves to neutralize the noise currents inthe input resonator, it does not itself control the beam currentdirectly because, due to the attraction of the anode 8, any electronwhich passes through the grid I will proceed to said anode. The secondresonator would, however, tend to neutralize any velocity modulation inthe beam so that this arrangement would be unsatisfactory in a circuitoperating with velocity modulation of the electron beam.

It will be appreciated from a consideration of the construction shown inFigures 1 and 2 that the two resonators 9 and I I, since they have acommon wall, will be maintained at the same direct current potential.This, however, is not necessary and is undesirable in some cases, sinceit does not permit the two resonators to be maintained at differentdirect current potentials. Thus, the construction shown in Figure 3 maybe employed, from which it will be seen that the resonator II is formedseparately from the resonator 9. The space between the resonators may befilled with dielectric material, if required, for constructionalreasons, leaving, of course, a suitable gap in the dielectric near thegrids for the passage of electrons. With such an arrangement it will beappreciated that the resonators may be maintained at difierent directcurrent potentials and that, if desired, the resonator II may bemaintained at a high positive potential so that the field produced dueto the high potential applied to the resonator II will serve to drawelectrons from the cathode, even though the grid I0 is at a negativepotential. Thus, the resonator II can efiectively perform the functionof the screen-grid of a conventional valve. If desired, as shown inFigure 4, the aperture in the resonator II may be provided with a gridI! or, alternatively, as shown in Figure 5, the aperture in theresonator remote from the aperture adjacent the grid I0 may be providedwith a grid I8. In a further form of the invention as shown in Figure 6,the resonator II is formed in two parts Ila and Ilb, which arecapacitatively coupled together through the medium of the peripheralflanges I9I9', which may be separated by air or vacuum or by adielectric substance it" if a higher capacity is required. In this casethe aperture in the portion I I?) may be provided with a grid 20 and theportion II a provided with a grid 2i and if the portion IIa ismaintained at a low potential, such as cathode potential, the grid 2Ican serve to prevent secondary electrons leaving the anode 8 so that thedevice can be made to function similarly to a conventional pentodevalve.

In all the arrangements shown in Figures 2 to 63, inclusive, of thedrawing, coupling means such as loop I is required and in Figure 1 loopsI 2 and I3 are required between the two resonators 9 and II.

The devices described may be employed for any suitable purposes, such asfor amplification, detection or mixing of high frequency oscillationsand although the output from the devices described is taken from theanode 8, it will be appreciated that, if desired, the beam of electronspassing through the hollow resonator Il may be 5 caused to pass througha further hollow resonator from which an output can be obtained. Wherethe device is employed for mixing oscillations the electron beam, afterleaving the resonator I I, may pass to a further system of any suitableform by which oscillations of a difierent frequency can be applied tothe beam so as to produce resultant oscillations of the differentfrequency.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it will be apparentthat my invention is by no means limited to the exact forms illustratedor the use indicated, but that many variations may be made in theparticular structure used and the purpose for which it is employedwithout departing from the scope of my invention as set forth in theappended claims.

What I claim as new is:

1. An electron discharge device having a cathode for supplying a beam ofelectrons and a collector for receiving said electrons, and a pair ofcavity resonators surrounding the electron path between the cathode andthe collector and through which the beam of electrons successivelypasses, and a reversed coupling loop extending between said resonatorswhereby noise currents set up by passage of the electron beam throughthe first resonator are reduced or substantially neutralized by thenoise current set up by the passage of the electron beam through thesecond resonator.

2. An electron discharge device having a cathode for supplying a beam ofelectrons and a collector for receiving said electrons, a firstresonator positioned adjacent said cathode and provided with a gridthrough which the electrons pass, and a second resonator surrounding the4.5 electron path between said first resonator and said collector, and areversed coupling loop extending between said resonators whereby thenoise currents set up by the passage of the electrons through the firstresonator is reduced or 50 substantially neutralized by noise currentset up by the passage of said electrons through the second resonator.

3. An electron discharge device including a cathode for supplying a beamof electrons, and a 55 collector for receiving said electrons, and afirst resonator surrounding said cathode and through which said electronbeam is directed, and a second resonator surrounding the electron pathbetween said first resonator and the collector and 60 having a commonwall with said first resonator,

said common wall being provided with an aperture and grid extendingacross said aperture, and

a reverse coupling loop extending between said resonators whereby noisecurrents induced in the 65 first resonator are substantially neutralizedby the same noise currents induced in said second resonator.

4. An electron discharge device having a cathode for supplying a beam ofelectrons and a col- 70 lector for receiving said electrons, a firstresonator adjacent said cathode and through which the electron beampasses, and a second resonator surrounding the electron path betweensaid first resonator and said collector, said resonators hav- 75 ingaligned apertures through which the beam of electrons successivelypasses, a reverse coupling 100p extending between said resonatorswhereby noise currents set up by the passage of electrons through thefirst resonator are reduced by noise currents set up bythe passage ofelectrons through the second resonator.

5. An electron discharge device having a cathode for supplying a beam ofelectronsand a collector for receiving said electrons, a first resonatoradjacent said cathode and through which the electron beam passes, and asecond resonator surrounding the electron path between said firstresonator and said collector, said resonators having aligned aperturesthrough which the beam of electrons successively passes, a reversecoupling loop extending between said resonators whereby noise currentsset up by the passage of electrons through the first resonator arereduced by noise currents set up by the passage of electrons through thesecond resonator, said second resonator comprising two parts, one ofwhich is adapted to have a positive voltage applied thereto and thesecond of which is adapted to have a lower voltage applied thereto tofunction as a suppressor, the two halves of said second resonator beingcapacitively coupled together.

CABO'I' SEATON BULL.

